Deep Venous Thrombosis patients experience clotting of blood in the large veins of the lower portions of the body. These patients are constantly at risk of a clot breaking free and traveling via the inferior vena cava to the heart and lungs. This process is known as pulmonary embolization. Pulmonary embolization can frequently be fatal, for example when a large blood clot interferes with the life-sustaining pumping action of the heart. If a blood clot passes through the heart, it will be pumped into the lungs and may cause a blockage in the pulmonary arteries. A blockage of this type in the lungs will interfere with the oxygenation of the blood causing shock or death.
In the case of venous disease, there are estimated to be over 2 million cases of deep venous thrombosis (DVT) in the U.S. each year. Only about 700,000 are diagnosed, and approximately 200,000 people die of pulmonary embolism, a complication of DVT, causing it to be the third leading cause of death in the U.S., more than breast cancer and AIDS combined. Sixty to seventy percent of patients with DVT eventually experience post thrombotic syndrome (PTS) as a result primarily of damage to the venous valves secondary from the cellular response and overgrowth because of the thrombus. Recurrent DVT will affect a large percentage of those who suffer from the initial episode, further compounding the problem. Therefore, millions of patients will suffer from the acute and chronic problems and health risks posed by DVT.
Thrombosis and atherosclerosis are common ailments which occur in humans and which result from the deposition of thrombus and clot on the walls of blood vessels. When hardened, such deposits are commonly referred to as plaque. Such deposits are most common in the peripheral blood vessels that feed the limbs of the human body and the coronary arteries which feed the heart. Stasis, incompetent valves, and trauma in the venous circulation cause thrombosis, particularly occurring as a deep vein thrombosis in the peripheral vasculature. When such deposits build-up in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk.
In addition to forming in the natural vasculature, thrombosis is a serious problem in “artificial” blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels requires anastomotic attachment at at least one, and usually at at least two, locations in the vasculature. Such sites of an anastomotic attachment are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arterio-venous grafts and fistulas which are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or, in the worst cases, a few months.
The human venous system in the lower extremities contains a number of one-way valves that function in allowing forward (antegrade) blood flow to the right atrium of the heart while preventing reverse (retrograde) flow to the feet. Using the muscle action of the calf to pump the blood, or the “peripheral heart,” the body is able to overcome gravitational forces to maintain blood flow back to the heart. The valves thus prevent blood from pooling in the lower extremities. Physiologically functioning valves are capable of withstanding very high proximal pressure gradients with minimal leakage, and can open at very low distal pressure gradients. However, for many patients, venous function is severely compromised by chronic venous disease (CVD), caused by Chronic Venous Insufficiency (CVI). Many times, CVI is a result of PTS caused by DVT events described above. Over seven million Americans suffer from CVI, a painful and debilitating disease that affects the superficial and deep veins of the legs. Problems associated with CVI include varicose veins, bleeding, ulcerations, severe swelling, deep vein thrombosis, and pulmonary embolism, which may lead to death.
In the venous system, there is also proliferative overgrowth of cellular material at anastomotic sites of the veins with arteries or grafts in the case of dialysis grafts and other surgeries. Most importantly, there is cellular ingrowth of smooth muscle cells into venous valves and the walls of veins after DVT, especially if the thrombus is not cleared quickly. This proliferative cellular response has some similarities to the cellular response that occurs in arteries. The venous valves are particularly affected by deep venous thrombosis and by the eventual cellular response which evolves into a tough and thickened tissue, and the valves become stiff and non-compliant causing them to become incompetent and allowing venous reflux to develop. The ongoing reflux results in venous hypertension, dilated veins, and a plethora of symptoms, including swelling of the lower leg, heaviness, pain, skin discoloration, and even skin ulcers. Collectively, the symptom complex occurring after episodes of DVT and caused mainly by the incompetent venous valves has been referred to as the Post Thrombotic Syndrome (PTS.) Strategies have been employed to remove the venous thrombosis early, by mechanical catheters and pharmacomechanical (mechanical catheters and lytic agents) treatments, and are generally successful and the incidence of PTS is much less than if treated by non invasive means. However, venous reflux still occurs in some of these patients, probably the result of residual thrombus on the valves after the majority of thrombus has been removed and the resulting cellular proliferation that ensues. The cellular ingrowth is a complicated series of events resulting in smooth muscle infiltration, collagen deposition, and fibroblast proliferation, amongst other features that renders the valve leaflet enlarged, stiff, and frequently fused to the vessel wall incapable of function or even being repaired.
The current methods of treating venous diseases including DVT and its complications, notably pulmonary embolism and PTS, are much less than satisfactory for several reasons. The most common method of treating DVT is to administer Heparin, an anticoagulant which does not dissolve the clot, but prevents additional clot from forming. Ninety-five percent of patients treated for DVT are currently treated with Heparin. Heparin administration is convenient and fairly easily done, although it can be expensive. This method relies on the body's inherent thrombolytic processes to dissolve the clot. The main problem with Heparin administration, however, is that all of the clot does not dissolve or it does not dissolve very quickly, and there is resultant residual clot and damage to the venous valves which will lead to PTS. Several studies have documented that there is a lesser incidence of PTS when the thrombus is removed early on in the course of DVT, before the valves are damaged, and that the incidence of recurrent DVT is lessened when the thrombus is removed early on.
In an effort to remove the thrombus early and prevent recurrent DVT and PTS, devices and methods have been invented to remove the thrombus. Initially, in the early 1980's systemic thrombolysis was attempted with a thrombolytic drug. While this method was partially successful, the incidence of bleeding intracranially and in the gastrointestinal (GI) tract was unacceptable. Later, in approximately 1990, a method of catheter directed thrombolysis was developed in which the thrombolytic drug was infused directly into the thrombus. This worked, but the bleeding complications prevented widespread adoption. Around 2000 or so, a procedure termed pharmacomechanical thrombolysis was utilized in which the catheter mechanically agitated the thrombus while the lytic agent was being infused. Again, the bleeding complications were a deterrent to use and even the mechanical action along with the lytic drug did not remove all of the thrombus in most cases. Subsequently, “isolated” pharmacomechanical thrombectomy was developed in which the lytic drug is contained within a section of the vein that is being treated, and most of the lytic drug does not enter the systemic circulation. This was an improvement, and the bleeding complications are lessened. These devices, however, are expensive and carry some risk to the patient, including bleeding, and are frequently not successful in removing all of the thrombus. In fact, the clot is removed completely in the minority of patients and only partially in others. This sometimes necessitates continuing the lytic therapy overnight or for several days in the intensive care unit which is expensive and adds the extra risk of systemic exposure to the lytic agent with subsequent bleeding. The continued lytic therapy raises the potential for bleeding in the GI tract, brain, and elsewhere. Hence, the added cost of the drug and the ICU monitoring and the added risk of protracted exposure to higher levels of the lytic drug is not only problematic to those patients treated in this manner, but they are also a deterrent to other patients even having the procedure which may help them avoid the long term sequelae of aggressive interventional therapy for DVT.
The main reason for subjecting the patient to the additional expense and risk of protracted lytic infusion is that the thrombolytic and thrombectomy devices designed to treat the thrombus within the veins do not remove all of the thrombus. It is well known and accepted in the medical field that these prior art devices only remove or dissolve acute thrombus. The subacute or chronic thrombus which is frequently present is resistant to thrombolysis and thrombectomy. The development of DVT is usually a slow progressive process, and the patient does not really know, and it cannot be determined with any degree of certainty, when the DVT began and, hence, how old the thrombus is, whether acute, subacute, or chronic. Therefore the treating physicians really don't know or have the means to determine if the thrombolytic and thrombectomy devices available to them will work or not. This unknown is a deterrent for using an invasive, potentially dangerous, and very expensive method that may help the patient, but may not. This unknown prevents many patients from receiving aggressive therapy that may be beneficial to them. Both the lack of success of the prior art devices and the fact that many patients are not treated because of this unknown leaves the patient with residual thrombus which demands further costly treatment methods and increases the risk of valvular damage which predisposes the patient to develop recurrent DVT, chronic venous insufficiency and PTS later. There is a need to provide devices and methods that will rid the patient of all of the thrombus, including the subacute and chronic thrombus that prevents adequate treatment in many cases.
Traditionally, pulmonary embolization may be prevented by the appropriate placement of a thrombus filter in the vascular system of a patient's body. Placement of the filter may be accomplished by performing a laparotomy with the patient under general anesthesia. However, intravenous insertion is often the preferred method of placing a thrombus filter in a patient's vascular system.
Intravenous insertion of a thrombus filter is less invasive and it requires only a local anesthetic. In this procedure, the thrombus filter is collapsed within a delivery catheter. The delivery catheter is introduced into the patient's vascular system at a point which is convenient to the physician. The delivery catheter is then fed further into the vascular system until it reaches a desirable location for filter placement. The thrombus filter is then released into the blood vessel from the delivery catheter.
In the treatment of Deep Venous Thrombosis, a thrombus filter is placed in the inferior vena cava of a patient. The inferior vena cava is a large vessel which returns blood to the heart from the lower part of the body. The inferior vena cava may be accessed through the patient's femoral vein.
Thrombus filters may be placed in other locations when treating other conditions. For example, if blood clots are expected to approach the heart and lungs from the upper portion of the body, a thrombus filter may be positioned in the superior vena cava. The superior vena cava is a large vessel which returns blood to the heart from the upper part of the body. The superior vena cava may be accessed through the jugular vein, located in the patient's neck.
Once placed inside a blood vessel, a thrombus filter acts to catch and hold blood clots. The flow of blood around the captured clots allows the body's lysing process to dissolve the clots.
The walls of the blood vessels are lined with a thin inner membrane or intima. When the securing/anchoring portions of a thrombus filter puncture this inner membrane, the body responds to a puncture of the intima with a process known in the art as neointimal hyperplasia. As a result, the punctured area of inner membrane is overgrown with a number of new cells. The securing portions of the thrombus filter are typically encapsulated with new cell growth (neointimal hyperplasia). Because the portions of the filter contacting the blood vessel wall become fixed in this way, it is impractical to remove many prior art filters percutaneously after they have been in place for more than two weeks.
There are a number of situations in which it may be desirable for a physician to remove a thrombus filter. If the physician determines that more effective filtering would occur with a thrombus filter in a different position, the physician may remove the original filter from its present positions and deploy a new filter in a new position. If the physician determines that the risk of blood clots forming is no longer present, it may be desirable to remove the thrombus filter completely. Thrombus filters are often used in conjunction with anticoagulation drugs. At some point, the physician may desire to discontinue the use of anticoagulation drugs. The physician may also want to remove the thrombus filter in conjunction with discontinuing the anticoagulation drugs. The removal of the thrombus filter from the patient eliminates any possibility that a complete occlusion will occur at the thrombus filter site. The removal of the thrombus filter also eliminates any possibility that the thrombus filter will become loose and migrate within the blood vessel. A loose thrombus filter is undesirable because it may migrate to a dangerous or life threatening position.
For a general background on thrombus filter technology and some of the tools and apparatus used involving thrombus filters, see U.S. Pat. No. 6,217,600 issued to DiMatteo on Apr. 17, 2001 (“DiMatteo”), the entire disclosure of which is incorporated herein by reference in its entirety.
Conventional implantable thrombus filters (also known as blood filters and/or IVC filters) employing a variety of geometries are known. Many are generally basket or cone shaped in order to provide adequate clot-trapping area while permitting sufficient blood flow. Also known are filters formed of various loops of wire, including some designed to partially deform the vessel wall in which they are implanted. Vena cava filters commonly include a core portion from which a plurality of wires radiate outwardly. The wires serve to filter clots from blood flowing through the vein. Various hook-like projections, barbs and the like have been suggested for use in holding the filter in place once the delivery catheter has been withdrawn.
Some traditional vena cava filters include the Vena Tech-LGM vena cava filter, the Bird's Nest vena cava filter, and the Simon-Nitinol vena cava filter. The Vena Tech-LGM filter is a conical filter made from a Phynox alloy, with longitudinal stabilizing legs in addition to the intraluminal cone. The Bird's Nest filter is a “nest” of stainless steel wire which is wound into the vena cava, while the Simon Nitinol filter is a two-stage filter made from nickel-titanium (NiTi) alloy with a conical lower section and a petal-shaped upper section. The TrapEase is a filter laser cut from a single tube of nitinol material and is formed with a symmetric double-basket configuration providing two levels of clot trapping.
Although vascular filters are widely used for capturing emboli in blood vessels, existing filter configurations suffer from a variety of shortcomings that limit their effectiveness. In one shortcoming, vascular filters are susceptible to clogging with embolic material. When a filter becomes partially or totally clogged, the flow of blood through the vessel may be substantially reduced or stopped completely. When this occurs, serious complications can arise and therefore the patient must be treated immediately to restore adequate blood flow. Because of the potential for clogging, existing vascular filters are typically manufactured with relatively large pores or gaps such that only large emboli, such as those with diameters of 7 mm or greater, are captured. The large pore size is necessary for reducing the likelihood of clogging due to smaller particles. Unfortunately, in certain cases, the passage of smaller emboli may still be capable of causing a pulmonary embolism or stroke. Accordingly, physicians and filter manufacturers are required to balance the risk of clogging against the risk of pulmonary embolism and/or stroke.
Traditional indications for filters are patients with deep venous thrombosis, and with a contraindication for anticoagulation, or patients with large floating clots in the iliac veins or IVC, with an imminent risk of embolism. Additional contraindications are young patients or patients with a transient problem that may cause PE not requiring a permanent filter. However, one important problem with many available intravascular filters in use is the non-retrievability of the devices, because while penetration of the retaining hooks of the filter into the lumen of the IVC is necessary for the proper securing of the device, in extreme cases and over time, over-penetration may impinge upon adjacent organs, leading to serious or even fatal complications. Further, with time the filter will be integrated into the aortic wall, making it unretrievable without causing significant damage to the vessel wall, particularly at the body of the basket. Accordingly, a vena cava filter capable of temporary deployment is desired to provide rapid protection against pulmonary embolism. However, as the condition producing blood clots is successfully treated, it may be desired to remove the filter from the vena cava.
Catheter-based mechanical thrombectomy devices provide an alternative treatment method for removing blood clots from a patient's vasculature. Thrombectomy devices are typically used for removing a thrombus that has formed in a blood vessel and has occluded the flow of blood.
See U.S. Pat. No. 7,803,171 issued to Uflacker on Sep. 28, 2010 (“Uflacker”) for a general background on thrombus filter technology and some of the tools and apparatus used involving thrombus filters, the entire disclosure of which is incorporated herein by reference in its entirety.
Some attempts have been made to develop thrombus filters that are retrievable and accurately positioned. For example, see U.S. Pat. No. 7,534,251 issued to WasDyke on May 19, 2009 (“WasDyke”) which discloses a retrievable vena cava filter of multiple elongated filter legs each having a hook portion configured to releasably secure the filter to the wall of a vessel, and an expandable member releasably connected to the filter. The filter legs may be biased to expand from a substantially straight configuration to an outswept, conical-shaped configuration when deployed in the vessel. The expandable member may include a plurality of securing members configured to pierce and secure the expandable member to the vessel wall. In some embodiments, the expandable member may comprise a bendable member interconnected to several tubular members. In other embodiments, the expandable member may comprise a coiled wire. In use, the expandable member may be utilized to compress the filter legs against the vessel wall. The entire disclosure of WasDyke is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,793,348 issued to Palmaz on Dec. 27, 1988 (“Palmaz”) discloses a vena cava filter for preventing migration of lower extremity venous clots into the pulmonary circulation. The Palmaz filter comprises a tubular body, the wall of which is partitioned by a slot pattern into a latticework rendering the tubular body radially expandable; a head piece, having a threaded receiving hole, circumferentially affixed to the distal end of said tubular body; and a plurality of tines affixed in substantially uniform circumferential spacing about the proximal end of said tubular body. In a filter intended for femoral vein introduction into the vena cava, the tines are elongated appendages having hooked terminal ends. In a filter intended for jugular vein introduction, the tines are short spikes. The filter is delivered to the inferior vena cava by catheter means introduced through a vein sheath positioned in the femoral or jugular vein. After location within the caval lumen, the tubular body of the filter is expanded by a balloon catheter contained within the lumen of the filter, thereby rendering the latticework wall surface of the tubular body into a filtering network mesh and affixing the expanded filter within the vena cava. After deployment of the expanded filter within the vena cava, the catheter means is withdrawn. The entire disclosure of Palmaz is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,832,055 issued to Palestrant on May 23, 1989 (“Palestrant”) discloses a blood clot filter which includes a central core wire extending along a central longitudinal axis and surrounded by a number of peripheral wires evenly spaced about the central core wire. A first connector connects the peripheral wires together at one end of the central core wire at a first fixed connection point. A second connector connects the peripheral wires together at a second connection point spaced apart from the first connection point, the second connection point surrounding the central core wire and being slidably secured thereto. The blood clot filter includes a one-way lock device permitting the second connector to slide along the central core wire toward the first fixed connector from a first position remote from the first connector to a second position proximate the first connector. However, the lock device prevents the second connector from returning from the second proximate position back to the first remote position. The portions of the peripheral wires extending between the first and second connectors initially extend generally along the central core wire. As the second connector is advanced from the first remote position to the second proximate position, the portions of the peripheral wires extending between the first and second connectors move radially away from the central core wire to a deployed position for forming a filter mesh. The entire disclosure of Palestrant is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,727,873 issued to Mobin-Uddin on Mar. 1, 1988 (“Mobin-Uddin”) discloses an embolus trap comprising an expansible article which is inserted in its collapsed condition in a passageway and which then opens and secures itself. The Mobin-Uddin device comprises a central hollow column carrying preferably two or more tiers spaced therealong of radially extending elongated filaments, pairs of which are connected at their outer ends to form loops. Each tier includes two or more such loops and the loops of one tier are positioned circumferentially between the loops of the next adjoining tier. At the outside ends, the filaments are formed into outwardly extending hooks backed by offsets, the latter limiting the penetration of the hooks into the wall of a passageway in which the device is implanted. The filaments are preferably made of metal wire or other filament with sufficient spring to permit them to be folded back against the central column while the device is inserted into a passageway and then, when released, to assume a radially-extended position within the passageway forcing their hooked ends against the passage wall. The device is inserted into a vein by a catheter of plastic tubing having a tubular capsule at its distal end containing the device in its collapsed condition. In the capsule, the filaments are forced against the central column and are relatively straight. When the embolus trap is ejected, its filaments spring outwardly in the vein tending to assume their semi-lunar curvature. A wire guide extends through the hollow central column of the device and out beyond the capsule. The wire guide has a flexible J-tip at its outer end which facilitates maneuvering and prevents securing in the wall of the vein. A hollow push rod which fits over the wire allows the catheter to eject the embolus trap from the capsule so that it travels along the wire guide to its destination. For maneuvering the capsule in place, a different type of hollow rod is provided which will not eject the embolus trap from the capsule. The entire disclosure of Mobin-Uddin is incorporated herein by reference in its entirety.
U.S. Pat. No. 6,258,115 issued to Dubrul (“Dubrul I”) describes a stent of varying porosity for use in vessels with bifurcations or side branches. The stent allows for scaffolding of the stenotic area but still allows for flow into the side branches. A distal protection system is also described. Also, Dubrul I discloses a procedure-oriented system for carotid stenting which reduces or eliminates the stroke potential during stent placement by positioning a fragment filteritrap/occluder downstream (distally) from where the stent is disposed within a bifurcated blood vessel such as the common carotid artery. The Dubrul I device includes both a single lumen, multi-porous stent and a bifurcated stent, both of which are operable for stenting the common carotid artery at its point of bifurcation. However, the Dubrul I device is designed for use against blood flow with the most open end on the proximal end and not optimized for use with blood flow with the most open end on the distal end.
U.S. Pat. No. 6,238,412 issued to Dubrul et al. on May 29, 2001 (“Dubrul II”), U.S. Pat. No. 6,695,858 issued to Dubrul et al. on Feb. 24, 2004 (“Dubrul III”), and U.S. Pat. No. 6,221,006 issued to Dubrul et al. on Apr. 24, 2001 (“Dubrul IV”), describe a catheter device for removal of a blockage in a passageway, such as a dialysis graft or in a body passageway. The devices of Dubrul II, III and IV include a traditional funnel-like catheter for reception and aspiration of the blockage and an occlusion engaging element supported on a wire that extends through the catheter. The devices include a braid device that expands against the blood vessel wall to stabilize the catheter and to prevent the occlusion from passing around the outside of the device; blood flow is also prevented from passing through the device.
U.S. Pat. No. 6,699,260 issued to Dubrul et al. on Mar. 2, 2004 (“Dubrul V”) describes a catheter device for removal of a blockage in a body passageway fitted with a multi-wing malecot expansion device. Similar to Dubrul II, III and IV, the Dubrul V device entirely blocks blood flow, and the targeted blockage, from passing around or through the device. Further, U.S. Pat. Pub. No. 2010/0114113 to Dubrul et al. published May 6, 2010 (“Dubrul VI”) discloses a catheter device for occlusion removal that blocks blood flow.
U.S. Pat. Pub. No. 2004/0260333 to Dubrul et al. published on Dec. 23, 2004 (“Dubrul VII”) and U.S. Pat. Pub. No. 2010/0030256 to Dubrul et al. published on Feb. 4, 2010 (“Dubrul VIII”) describe a collection of funnel catheters, catheter/dilator assemblies, occluders, and associated methods which either entirely block blood flow or do not allow a controlled, predictable adjustment of allowed blood flow.
The entire disclosures of each of Dubrul I through Dubrul VIII are incorporated herein by reference in their entireties.
The prior art thrombus filter techniques or technologies do not provide a minimal-trauma device that enables predictable and reliable positioning, readily allow repositioning, are easily inserted and retracted, capable of removing all thrombus, including subacute and chronic thrombus. Also, traditional thrombus filters techniques or technologies do not allow pulling or moving of thrombus and/or shredding thrombus.
A variety of methods and devices have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature, as well as in implanted grafts and fistulas. Such devices and techniques attempt to filter, capture, pull and/or shred thrombus. Techniques include surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty, atherectomy, transmyocardial revasculaturization, and the like. Techniques generally described as “thrombectomy” have been developed. Thrombectomy generally refers to procedures for the removal of relatively soft thrombus and clot from the vasculature. Removal is usually achieved by mechanically disrupting the clot, optionally with the introduction of thrombolytic agents. The disrupted thrombus or clot is then withdrawn through a catheter, typically with a vacuum or mechanical transport device.
Thrombectomy generally differs from angioplasty and atherectomy in the type of occlusive material which is being treated and in the desire to avoid damage to the blood vessel wall. The material removed in most thrombectomy procedures is relatively soft, such as the clot formed in deep vein thrombosis, and is usually not hardened plaque of the type treated by angioplasty in the coronary vasculature. Moreover, it is usually an objective of thrombectomy procedures to have minimum or no deleterious interaction with the blood vessel wall. Ideally, the clot will be disrupted and pulled away from the blood vessel wall with no harmful effect on the wall itself.
While successful thrombectomy procedures have been achieved, most have required comprise between complete removal of the thrombosis and minimum injury to the blood vessel wall. While more aggressive thrombectomy procedures employing rotating blades can be very effective at thrombus removal, they present a significant risk of injury to the blood vessel wall. Alternatively, those which rely primarily on vacuum extraction, together with minimum disruption of the thrombus, often fail to achieve sufficient thrombus removal.
For example, U.S. Pat. No. 6,660,014 issued to Demarais on Dec. 9, 2003 (“Demarais I”) provides apparatus, systems, methods, and kits for removing occlusive material from body lumens. Demarais discloses a macerator for breaking up or “disrupting” the thrombus, clot, or other occlusive material, where the macerator is positioned to minimize or prevent contact with and reduce or eliminate the potential for injury to the luminal wall. The device comprises a catheter for removing the occlusive material from the body lumen. The catheter comprises a catheter body having a proximal end, a distal end, and a lumen therethrough. A radially expansible positioning cage is disposed on the catheter body near its distal end, and a macerator is disposed within the expansible positioning cage. The macerator is configured to disrupt occlusive material within the cage when the cage is expanded against the luminal wall. The macerator is typically a rotating element, such as a helical or other shaped wire which engages and disrupts the occlusive material. Usually, the disrupted material will also be drawn into the catheter body lumen. Alternatively, the disrupted thrombus can be captured, in whole or in part, by a second catheter usually introduced downstream from the first catheter with the macerator. The second catheter may also comprise a macerator and, in some instances, the two catheters can be similar or identical. In all cases, the disrupted thrombus may be removed through the catheter lumen by aspiration using an external vacuum source and/or a mechanical pump. U.S. Pat. No. 6,945,977 issued to Demarais on Sep. 20, 2005 (“Demarais II”) provides additional embodiments of the devices and methods of use to that of Demarais I. Both Demarais I and Demarais II are incorporated herein by reference in their entireties.
U.S. Pat. No. 7,686,825 issued to Hauser on Mar. 20, 2010 (“Hauser”) provides a vascular filter device adapted for capturing and breaking down embolic material from the blood. The Hauser device generally comprises a filter body sized for deployment in a blood vessel and an agitation member movably coupled to the filter body. During use, movement of the agitation member acts to break apart particles captured within the filter body. To reduce the possibility of filter migration, the filter body may be provided with anchoring elements for engagement with an inner wall of the blood vessel. The anchoring elements may comprise penetrating tips, barbs, hooks or any other structure configured to engage the inner wall. In another variation, the filter device may be supported by a stent structure that expands for engagement with the inner wall.
The venous system of the legs uses valves and muscles as part of the body's pumping mechanism to return blood to the heart. Venous valves create one way flow to prevent blood from flowing away from the heart. When valves fail, blood can pool in the lower legs, resulting in swelling and ulcers of the leg. The absence of functioning venous valves can lead to chronic venous insufficiency.
The presence of CVI results from damaged (incompetent) one-way vein valves in leg veins. These valves normally allow forward flow of blood to the heart, and prevent blood from pooling at the feet. However, incompetent valves allow reflux of blood, causing clinical problems. There are few effective clinical therapies for treating CVI other than compression stockings and elevating the leg. Vein valve transplantation is a surgical option for treatment. However, it is often difficult to find suitable donor valves. Very few prosthetic valves developed in the past have demonstrated sufficient clinical or mechanical functionality. Persistent problems include thrombus formation, leaking valves, and valves that do not open at physiologic pressure gradient. There is a rather uniform problem of fibrin deposition on the foreign substance constituting the prosthetic valve. There has yet to be a prosthetic venous valve developed that has demonstrated the necessary functional performance for operating satisfactorily in human physiologic conditions. While various designs have been pursued in the past, many such designs possess shortcomings that prevent them from being a sufficiently functional design.
Techniques for both repairing and replacing the valves exist, but are tedious and require invasive surgical procedures. Direct and indirect valvuoplasty procedures are used to repair damaged valves. Transposition and transplantation are used to replace an incompetent valve. Transposition involves moving a vein with an incompetent valve to a site with a competent valve. Transplantation replaces an incompetent valve with a harvested valve from another venous site.
Prosthetic valves can be transplanted into the venous system, but current devices are not successful enough to see widespread usage. One reason for this is the very high percentage of prosthetic valves reported with leaflet functional failures. These failures have been blamed primarily on improper sizing and tilted deployment of the prosthetic valve. In addition, a great number of leaflets of the prosthetic valves ultimately become fused to the vein wall.
A typical traditional prosthetic venous valve is provided in U.S. Pat. No. 7,569,071 issued to Haverkost et al. on Aug. 4, 2009 (“Haverkost I”) which discloses venous valve frames, venous valves that utilize the venous valve frames, and methods for forming and using the venous valve frame and the venous valve. Various embodiments can be used to replace and/or augment an incompetent valve in a body lumen. Embodiments of the venous valve include a venous valve frame and valve leaflets that can be implanted through minimally-invasive techniques into the body lumen. In one example, embodiments of the apparatus, system, and method for valve replacement or augmentation may help to maintain antegrade blood flow, while decreasing retrograde blood flow in a venous system of individuals having venous insufficiency, such as venous insufficiency in the legs. U.S. Pat. No. 7,951,189 issued to Haverkost et al. on May 31, 2011 (“Haverkost II”) provides additional embodiments of the devices and methods of use to that of Haverkost I. Haverkost I and Haverkost II are incorporated herein by reference in their entireties.
U.S. Pat. No. 7,670,368 issued to Hill et al. (“Hill I”) on Mar. 2, 2010 discloses an apparatus, system, and method for valve replacement or augmentation. The apparatus can include a valve that can be used to replace or augment an incompetent valve in a body lumen. Embodiments of the valve can include a frame and cover that can be implanted through minimally-invasive techniques into the body lumen. In one example, embodiments of the apparatus, system, and method for valve replacement or augmentation may help to maintain antegrade blood flow, while decreasing retrograde blood flow in a venous system of individuals having venous insufficiency, such as venous insufficiency in the legs. U.S. Pat. No. 7,867,274 issued to Hill et al. on Jan. 11, 2011 (“Hill II”) provides additional embodiments of the devices and methods of use to that of Hill I. Hill I and Hill II are incorporated herein by reference in their entireties.
U.S. Pat. No. 7,780,722 issued to Thielen et al. (“Thielen”) on Aug. 24, 2010 provides a venous valve with a frame and a cover on the frame for unidirectional flow of a liquid through the valve quite similar to that of Hill I and Hill II. Thielen is incorporated herein by reference in its entirety.
Some attempts have been made to develop venous devices useful and adaptable for multiple applications, see U.S. Pat. No. 5,632,754 issued to Farley et al. on May 27, 1997 (“Farley”), the entire disclosure of which is incorporated herein by reference in its entirety.
Typically, the stability of the catheter tip is problematic and critical to the medical procedure. In many cases a “guide” catheter is inserted and the tip is placed within or near the orifice of the vessel intended to be treated. See for example U.S. Pat. No. 5,947,995 issued to Samuels on Sep. 7, 1999 (“Samuels”), the entire disclosure of which is incorporated herein by reference in its entirety.
For a general background on stenting and guiding catheters, see U.S. Pat. No. 7,645,296 issued to Theron et al. on Jan. 12, 2010 (“Theron”), the entire disclosure of which is incorporated herein by reference in its entirety.
Several devices have been used to place a filtering device into the inferior vena cava using a transvenous route, commonly originating from the right jugular vein or from either femoral vein. For example, the method disclosed in U.S. Pat. No. 3,834,394 to Hunter, et al., (“Hunter”) uses a detachable balloon which is delivered to the inferior vena cava at the end of a catheter. The balloon and catheter are inserted into one of the veins in the neck using a surgical incision and passed to the lower inferior vena cava where the balloon is inflated. Once detached, the balloon occludes the inferior vena cava entirely, thereby preventing any flow of blood or blood clots to the heart. While insertion of this device avoids major abdominal surgery, it still requires a small surgical procedure to be performed in order to expose a neck vein. The balloon occludes the inferior vena cava completely, resulting in swelling of the lower extremities until collateral circulation develops around the balloon. With time, these collateral channels may become large enough to permit life threatening emboli to pass to the lung. The entire disclosure of Hunter is incorporated herein by reference in its entirety.
Another device for preventing pulmonary embolism but which does not require total occlusion of the inferior vena cava is an implantable cone-shaped filter device consisting of six spokes with sharpened points at the end and connected together at the other end by a central hub. A thin membrane with 4 mm holes covers the device. The umbrella-like device is folded into a cylindrical capsule connected to the end of a catheter. This device is described in U.S. Pat. No. 3,540,431, to Mobin-Uddin (“Mobin-Uddin”). This device also requires a surgical cutdown on a major right neck vein for access to the venous system. The device and delivery capsule are positioned in the inferior vena cava and released by pushing the device out of the capsule. While the device acts as an efficient filter, approximately 60% of patients using the Mobin-Uddin filter develop occlusion of the inferior vena cava, sometimes resulting in severe swelling of the legs. Furthermore, instances of migration of the filter to the heart have been reported; such instances present a high mortality risk. The entire disclosure of Mobin-Uddin is incorporated herein by reference in its entirety.
U.S. Pat. No. 3,952,747, to Kimmel (“Kimmel”), discloses a blood vessel filter and filter insertion instrument which overcome some of the disadvantages of the previous two devices. The Kimmel patent describes a device which may be inserted either from the jugular or femoral approach using a surgical exposure of a major vein. The conical shaped device consists of six strands of wire each connected to a hub at one end and having recurved hooks on the other end. The device is loaded into a cylindrical delivery capsule which is connected to a catheter. The delivery capsule measures 6 mm in diameter and 5 cm in length. Because of its size, a surgical exposure of the vein is necessary for introduction of the delivery capsule into the vascular system. More recently, the delivery capsule has been introduced into the vascular system through a large catheter using angiographic techniques. However, this technique has been shown to significantly injure the vein at the introduction site. Sometimes it may not be possible to pass the capsule from below through tortuous pelvic veins into the inferior vena cava because of the inflexibility of the capsule. The filter engages the wall of the vein at one end and therefore often tilts to one side. It is very difficult to deliver the filter in a manner that maintains the longitudinal axis of the filter centered along the longitudinal axis of the vena cava. A tilted filter has been shown to be less efficient at capturing blood clots. Migration of the filter has not been a problem. The entire disclosure of Kimmel is incorporated herein by reference in its entirety.
Another method of preventing pulmonary emboli from reaching the lungs is a device disclosed in U.S. Pat. No. 4,425,908, to Simon (“Simon”). This device uses the thermal shape memory properties of Nitinol to deploy the filter following delivery. The filter consists of seven wires banded at one end and also in the middle. The wires between these two points form a predetermined filter mesh derived from the thermal memory. The free-ends of the wires form anchoring points which radially engage the inferior vena cava. The device may be inserted through a jugular or femoral vein approach using standard angiographic catheters. The device relies on the thermal shape memory properties of the Nitinol wire to form an effective filter following delivery. The entire disclosure of Simon is incorporated herein by reference in its entirety.
U.S. Pat. No. 4,494,531, to Gianturco (“Gianturco”), also discloses a blood vessel filter which can be inserted through angiographic catheters. The device consists of a number of strands of wire which are interconnected and wadded together to form a curly wire mesh. The filter includes a number of projections which serve as an anchoring means for anchoring the filter at a suitable body location within the inferior vena cava. Problems with the device include migration and demonstration invitro of filtering inefficiency. The random nature of the filtering mesh makes it difficult to assess the overall efficacy. Perforation of the anchoring limbs through the vena cava has also been described. The entire disclosure of Gianturco is incorporated herein by reference in its entirety.
The use of the above devices can be cumbersome, time-consuming and expensive. Furthermore, these devices do not adequately capture emboli in the blood or remove all thrombus, such as subacute and chronic thrombus. Rather, these devices are typically used to remove a thrombus that has formed within a vessel. In certain cases, these devices may actually produce emboli and cause a stroke or PE. Still further, the contact surfaces or fluid pressures of these mechanical thrombectomy devices may produce a variety of undesirable side effects, such as endothelial denudation and hemolysis. These devices are difficult to position and, in the case of venous valves, unreliable and generally ineffective. Therefore, an urgent need exists for minimal trauma devices and methods for capturing and/or completely removing blood clots from a patient's vasculature and for safely and effectively inserting prosthetic venous valves into a patient's vasculature. The present invention addresses these needs.
The use of the instant inventions and methods are, in the case of venous disease, designed to treat DVT by removing acute, subacute, and chronic thrombus, preventing pulmonary emboli, removing pulmonary emboli, preventing the smooth muscle cell migration and population into the valvular structure which causes valvular incompetence, repairing damaged veins and venous valves, and percutaneously placing prosthetic venous valves.